Water Disinfection using UV Reactors

      Water disinfection using UV irradiation has emerged in the past years as a good alternative due to growing concerns with chlorinated by-products and safety of measuring chlorination. It is known that the performance of UV reactors is determined by distribution of UV dose, defined as the product of hydraulic residence time and light irradiance intensity. However, information for  hydraulic residence time for evaluating hydraulic performance of UV reactors are limited. In this project a real time 2D digital particle image velocimetry is used to measure velocity distribution in two UV reactors, UV-SWIFT and UV-MAX. Turbulence, Reynolds stresses, dissipation, and vorticity at the regions of the wall of the reactor and the near-far fields of the UV lamps are characterized for the purpose of calibrating and verifying the models of UV reactors. We are currently working on characterization of mixing and 3D turbulent motions using laser-induced flow visualization and 3D particle image velocimetery. In addition, a flunet CFD software is used to examine irradiation efficicay of UV disinfection process


 
                             Raw image                                                      Velocity and Vorticity                                                              UV-MAX
 
      Excessive growths of blue-green algae (cyanobacteria) are a common problem in eutrophic (fertile) lakes world-wide. Many blue-green algae species (including non-scum formers) can also produce hepato- or neuro-toxins of health concern to humans and other warm-blooded animals. Thus, beaches and swimming areas on certain shorelines can periodically experience large densities of blue-green algae that are not only unaesthetic, but potentially harmful to human health. In collaboration with City of Madison, Dane County, and Department of Natural Resources, we have tested a variety of devices, called algal scum interceptor, deflector, and exclosure (ASIDE) system, to reduce the presence of algal scums at several public beaches. One of the effective devices is an enclosure at Brittingham Beach and Bernie Beach, Monona Bay. The exclosure consists of a flotation collar and full water depth curtain. The full water depth curtain provides a mean to separate the lake water from the inside beach water as to exclude unsafe lake water from contaminating the swimming area. Furthermore, a treatment system is used to pump water inside the swimming area which filters and disinfects beach water using a series sand filter and UV system. The clean, treated water is then returned to the swimming area while algae and other unwanted materials are backwashed based on system pressures to the sanitary sewer. To provide real-time information and test its effectiveness, a Real Time Water Imaging System (RTWIS) is currently developed.